The present invention relates to improvements in endodontics or root canal therapy. More specifically, it relates to processes of devitalization of teeth as well as the means of practicing the process.
The "devitalization" of a tooth by removal of the pulp and replacement with an inert cement-like substance, is an extremely common operation in dental surgery. Despite advances in dental therapeutics and anesthetics, root canal surgery can be a painful experience for the patient. The term "root canal surgery" or "devitalization" means extraction of the pulp or a pulpectomy. Dental pulp is the richly vascularized innervated connective tissue contained in the pulp cavity of the tooth. It constitutes the formative, nutritive and sensory organ of the dentin. Pulp contains nerves and many vessels such as arteries, veins and lymph vessels and is composed chiefly of cells and connective tissue. Pulp is appreciably softer than the outer enamel and the dentin and consists primarily of a layer of cells (odontoblasts) which secrete the secondary dentin onto the interior wall of the tooth. The pulp terminates at the bottom of the tooth in a funnel or apex shape.
Under normal circumstances, the pulp is protected from infection. However, infections can arise when decay or caries spreads through the enamel and dentin or when fillings crack and expose the soft tissue. Infections may also arise when the tooth is dislodged or suffers trauma. If the infection remains untreated there is a serious risk of the infection spreading through the tooth's roots into the supporting bone structure. The usual procedure in endodontics is to remove the infected pulp and/or the damaged nerve, followed by sterilization of the tooth's roots. Finally, the area is sealed with an inert paste to protect it from future infections.
One method of devitalization consists of the use of an arsenic compound, As.sub.2 O.sub.3, which acts by vasodilation. The dilation of the arteries causes a constriction of the veins so that the blood can no longer circulate. Once circulation ceases, necrosis of the tissue commences.
As soon as necrosis is achieved, a wide opening in the upper surface of the tooth is formed. Instruments such as a broach, a barbed broach and files are used in root canal surgery. Once the opening in the tooth is of sufficient size, an inert paste is introduced by means of a lentula (small endless screw) which is designed to force the paste into the cavity. One of the drawbacks in the use of the barbed broach is that it extirpates the pulp, causing a tissue laceration.
A second commonly employed method of root canal surgery is almost identical to the first, except that the first stage of the process consists of administering a local anesthetic such as lidocaine, instead of the use of the arsenic compound. The anesthesia usually makes it possible to conduct the necessary dental operations without the patient experiencing intolerable pain. However, because of the mechanical aggravation of the dental tissue caused by the surgery, patients frequently suffer continued pain once the initial anesthesia abates. Thus, the surgeon is often obliged to prescribe further pain relievers to reduce the patient's discomfort.
The canals present in the tooth are extremely contorted in shape (elbows, reverse elbows, bayonets, etc.), so that it is not always possible to completely fill the canals with the inert paste. Because of the contorted shape of many canals, broaches are employed to ream the canal and straighten it. Frequently, files also have to be used to straighten the canal. Once the canal has been straightened, the soft tissues can be replaced with the inert hard paste. Prior to introduction of the paste into the cavity, it is necessary to completely dry the cavities to be filled. Paper cones are usually employed for this purpose.
The paste used in root canal surgery is hydrophobic, and comprises a base consisting of a radiopaque powder and a biocompatible oil. Accordingly, in order to obtain a good tight filling with the paste, it is imperative for the cavity to be perfectly dry. The paper cones dry the canals by a kind of pumping action. The inert paste is then placed into the pulp chamber and is forced into the channels by means of lentulas (endless screws) which force the paste into the cavity. To avoid air bubbles, cones of gutta-percha, resin, silver, etc., are placed inside the canal.
In current dental practices in the United States, the lentula is not used. Instead the canals are enlarged. Gutta-percha is then placed in the canals and is heated, which causes the gutta-percha to melt and condense along the canal walls. Unfortunately, this is time intensive and takes from one hour to an hour and a half for each canal. An electrically powered and heated endodontic syringe for this purpose is disclosed, for example, in U.S. Pat. No. 4,684,344. In this patent there is disclosed a syringe which includes a drive motor and mechanism for translation of a plunger, a gutta-percha cartridge and heating element surrounding the cartridge.